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• �r Pre-Tank Relining Site Assessment Report 4 The Southland Corporation 4501 North Pershing Avenue Stockton California February 28, 1997 any of the eight soil samples collected. Total lead was"reported in four soil samples at concentrations ranging from 11 to 13 mg/kg. Copies of laboratory analyses reports and chain-of-custody manifests are included in Appendix C. 3.3 Results of Groundwater Sample Analyses Table 2 summarizes the laboratory analytical results for groundwater samples collected from soil borings, GP3, GP4, and GP7 on February 20,1997. A sheen was noted on the water sample GP4, and the sample also contained the highest concentrations of BTEX, MTBE, and TPH-G of the three sampled wells. The water sample collected from,GP3, located immediately north of the tank pit, contained significantly lower concentrations of benzene,TPH-G, and MTBE than GP4. Water sample GP-7, collected from a point located upgradient of the USTs; did.not contain concentrations of BTEX, MTBE, or TPH-G above'the laboratory reporting limit. Maximum concentrations in groundwater sample GP4 were benzene at 9,100 ug/L, TPH-G at 1.00,000 ug/L, and MTBE at 100,000 ug/I using EPA method 8020. The concentration of MTBE in sample GP4 was . confirmed using EPA method 8260 at 84,000 ug/L. Copies of laboratory analyses reports and chain-of- custody manifests are included in Appendix C. 4.0 SUMMARY AND CONCLUSION. A total of seven geoprobe points were drilled at the subject site: four angled borings to vertical depths of 15 feet under the three USTs,two vertical borings to a depth of 22 feet adjacent to the USTs, and one vertical . boring to a depth of 22 feet in the southeastern corner of the property(Figure 2). A total of eight soil samples and three groundwater samples were.collected for analysis. No TPH-G was detected in the eight soil samples analyzed; one sample contained benzene; and four samples contained'MTBE (Table 1). Elevated concentrations of benzene;MTBE, and TPH-G were detected in groundwater samples GP3 and GP4 collected immediately north and east of the USTs. The upgradient water sample GP-7 did not contain reportable concentrations of BTEX,TPH-G, or MTBE. Due to the elevated hydrocarbon concentrations in the groundwater samples collected near the USTs, an. . Underground Storage Tank Unauthorized Release (Leak)/Contamination Site Report was completed by the SJCPHS. The down-gradient and cross-gradient limits of the impacted groundwater were not defined. Since the USTs are located five feet west of the sidewalk,the impacted groundwater plume extends off site northeast of borings GP3 and GP4. 0472ASMT.RPT(Sthl-56) FLUOR DANIEL GTI